A number of studies designed to elucidate the molecular basis of neuronal cell surface recognition will be carried out. Detailed studies of adhesive specificity between embryonic cells of various neuronal regions will be made using a newly developed assay. The hypothesis that differential cell adhesion is related to synaptogenesis will be tested directly. Attempts will be made to screen for clonal neuronal lines which are capable of recognizing cells of the normal nervous system. If such lines are obtained they will be used in attempts to purify and characterize the composition and mode of action of purified cell- cell-receptors. Finally, tissue culture preparations capable of yielding reasonable quantities of defined classes of axons will be developed. The axons will be tested for adhesive elements.